1. Field of the Invention
This invention relates to forming temporary airborne images. In particular, this invention relates to forming temporary airborne images that may act as decoys for homing missiles and the like.
2. Discussion of the Background Art
Large targets, such as war ships, are prone to damage by attack from airborne missiles provided with homing capabilities that may include thermal or image sensing devices for maintaining the missile on target to impact the target. War ships are generally provided with defensive weaponry for combating incoming missiles by targeting the incoming missile with multiple rounds of munitions such as by a phalanx system. However such missiles may prove difficult targets and even a successful encounter with an incoming missile may be very costly in terms of resources and operational personnel.
We have now found a method of forming a temporary airborne image that acts as a decoy for homing missiles, guided airborne weapons and the like.
Accordingly the present invention provides a method of decoying an incoming missile from a target by forming a temporary image, said method including the steps of arranging a plurality of projectiles in each bore of one or more barrel assemblies wherein each projectile includes a body and a trailing collar captively mounted to the projectile body for operatively sealing with a respective bore, and wherein said projectiles include image forming matter for mimicking a homing characteristic of the target, firing a predetermined number of the plurality of projectiles from selected barrel assemblies, and deploying the image forming matter to form a temporary image and decoy the incoming missile from the target.
This invention may utilise barrel assemblies capable of firing a controlled rapid fire sequence of mortar like projectiles and being of the general type described and/or illustrated in earlier International Patent Applications by the present inventor, such as PCT/AU94/00124, PCT/AU00/00296 and PCT/AU00/00297. In at least some of these earlier applications, including the earliest filed International Application No. PCT/AU94/00124 there are described arrangements for grouping barrels each containing a plurality of projectiles so that a large number of projectiles can be fired in rapid-fire succession. In such arrangements barrels may be formed from a cylindrical shell having a plurality of projectiles axially disposed within the shell for operative sealing engagement with the bore of the shell and discrete propellant charges for propelling respective projectiles.
Suitably the barrel assemblies may be of the low pressure type which fire grenade-like projectiles although high muzzle pressure barrel assemblies may be used. Respective barrel assemblies may be loaded with different projectiles and the barrel assemblies may have different size bores for accommodating different size projectiles.
Suitably each projectile includes a trailing collar captively mounted to the projectile body and when stored in the barrel, extends rearwardly to wedge against the nose portion of a trailing projectile body. Suitably the wedging action is provided by a shallow wedge whereby, in use, the trailing end of the collar is expanded into operative sealing engagement with the barrel.
The trailing collar may be mounted for limited axial movement relative to the projectile body and the leading end of the collar formed with an annular sealing face engageable with a complementary face formed on the projectile body whereby rearward movement of the projectile body resulting from the reaction of the propellant gases thereon forces its complementary face into sealing engagement with the annular sealing face at the leading end of the collar.
The complementary face and the annular sealing face may extend substantially radially and be formed with complementary sealing features thereon. However it is preferred that these faces are complementary part-conical sealing faces which wedge into tight sealing engagement with one another. The leading end part may also be expandable into operative sealing engagement with the barrel. Suitably however the wedging between the part-conical faces are relatively steep faces whereby the leading end of the collar is not expanded into operative sealing engagement with the barrel by the wedging action.
Preferably, each projectile is associated with a high pressure propellant chamber which exhausts to respective low pressure propulsion chambers formed between the adjacent projectiles for efficient low muzzle velocity operation. The high pressure propellant chambers may be formed integrally with the projectile body or the trailing collar or be provided at the exterior of the barrel to communicate therewith through ports provided through the barrel wall.
The image forming matter may include, for example, explosive matter, incendiary matter, incandescent or luminous matter or other matter to provide a highly visible temporary image, radar image and/or a thermal image for mimicking a homing characteristic of the target. For example, in order to decoy a thermal image homing missile a thermal image may be provided to deceive the incoming missile to detonate on the thermal image of the target leaving the target substantially intact.
Alternatively, the image forming matter may include smoke, gas, particles or sheets or strips, such as in the nature of chaff or similar radar reflective matter, or other material capable of being dispersed to form an image. The image forming matter may also include means for slowing its descent from its dispersed position, such as a parachute and the like.
The projectiles are arranged in the barrel assemblies such that once fired and the image forming matter deployed, the desired temporary airborne image is formed. Projectiles containing different image forming matter may be sequentially loaded into each barrel assembly.
The projectiles may be electronically fired at an infinitely variable frequency up to the maximum rate of fire. For firing from a barrel assembly according to an aspect of this invention and arranged for low pressure, low muzzle velocity, the rate of firing is limited by the time taken for each projectile to leave the barrel and by the time necessary for the gas pressure in the barrel to drop sufficiently to enable the firing of the next projectile.
The predetermined number of the plurality of projectiles may be fired from selected barrel assemblies at a rate selected to obtain the desired temporary airborne image. The firing of the projectiles may preferably be controlled by a microprocessor to permit the accurate firing of the projectiles at the selected rate.
The image forming matter may be deployed, for example, by explosive means, by stored energy or by separation of separable parts of the projectile to expose the image forming matter or by any other suitable dispersing means.
A timing mechanism to control the deployment may be of any suitable type and may be clock based or based on a flight characteristics of the projectile such as the number of spins of a projectile fired from a rifled barrel or it may be based on the ambient atmospheric conditions at the selected display position. Alternatively, the timing mechanism may selectively control the timing of deployment of parachutes associated with the image forming matter.
The image may be formed as an upright image or a horizontal image and may include either or both image forming matter which leaves a visible trail during descent and image forming matter which does not leave a visible trail during descent. The former may be used to provide a coloured background or a stripe or the like while the latter may provide feature within the image such as a bright star-like image.
The projectiles may be configured to disperse the image forming matter at a set time from firing and the firing may be controlled for trajectory or barrel exit velocity so that upon dispersal of the image forming matter the desired displayed is achieved. Alternatively a barrel assembly may contain respective projectiles adapted to produce different image effects and the desired image may be controlled by selectively firing the projectiles to assemble an in-air compilation of different image effects to achieve the desired image.
For the purpose of the decoy images the projectiles may be fired to provide a general zone having either the necessary extent or thermal or visual characteristics so as to trigger a missile directed at the vessel or installation being defended. Alternatively, the projectiles may be fired to produce a shape which mimics the shape of the vessel or installation being defended, so as to appear to the missile to be the vessel or installation being defended.
A bank of barrel assemblies may be utilised containing respective image forming matter which may be selectively fired and, if desired at a desired trajectory or timing, the barrel assemblies being controlled remotely such as from a computer keyboard and screen which may show a preview of the image to be formed and enabling an operator to xe2x80x9cprintxe2x80x9d a desired or random airborne pattern. The image may be a two or three dimensional image as desired. Different banks of barrel assemblies may be utilised and/or placed so as to form a respective unique portion of the image being formed.
A direction control means may be provided in a bank of barrel assemblies and may permit uniform pivoting of the barrel assemblies so that the inclination of the axes of the barrel assemblies relative to the axis of a pod containing the bank of barrel assemblies may be selectively varied to enable a target position relative to the pod to be varied. The direction control means may permit individual pivoting of each barrel assembly so that the inclination of each barrel axis relative to a pod. axis may be individually varied to enable a target position or individual target positions relative to the pod to be varied. Such individual control may be associated with individual firing control of each barrel assembly if desired.
The direction control means may alternatively permit a controlled splaying of all barrel assemblies so that the area covered at the target zone may be selectively varied. Alternatively the direction control means may permit all or some of the above variations to be achieved individually or collectively as required.
The pod housing may be of any suitably configuration and may taper towards its base to enable barrel assemblies to be supported in a splayed attitude. The support means may be fold out legs which may be adjustable if desired. In one form the pod has a rectangular pod housing for economy or ease of storage and/or transport and the base thereof constitutes the support means.
A pod of barrel assemblies may be fired from a marine platform. The pod may also be fired from an aircraft, or from a number of aircraft flying in formation and if desired, with the firing coordinated between the aircraft by a suitable electronic link. The image could be formed parallel to the firing path, such as by projecting projectiles different distances so as to span the length of the image to be formed. Alternatively, the image could be created at right angles to the firing path by splaying projectiles to deploy across the desired span of the desired image. Thus even though there may not be a clear line of sight between a deck mounted pod containing the barrel assemblies utilised to create the image and an incoming missile, the image can be created at right angles to the incoming path of the missile.